Device for inspecting, sampling or extracting at a precise spot beneath a slab

ABSTRACT

A tool ( 7 ) for sampling or extracting the contents of a pit ( 4 ) is suspended from a cable ( 8 ) passing through a narrow opening ( 3 ) in a slab ( 2 ) covering the pit. A crosspiece ( 13 ) hooked to guide cables ( 11 ) which converge on it makes it possible to displace the lifting cable ( 8 ) under the slab ( 2 ) according to different movements imposed by winches ( 10 ). Thus it is possible to move the tool ( 7 ) to the desired point with great precision and without having to descend into the pit ( 4 ).

BACKGROUND OF THE INVENTION

The present invention relates to a device for examination, sampling orextraction at a precise point under a slab, and can be applied inparticular to dangerous products emptied for long-term storage in siloswhose ceiling is formed by a protective cover-slab pierced by a singleopening, generally in the centre, and normally closed.

When a sampling or examination of a sample of the contents of the silois decided, in the present state of the art it is normal to lower anappropriate mechanism suspended from a support cable into the silothrough the opening. The mechanism can be a grab in the case of solidsamples or an agitating and pumping unit for liquid or loose samples.But thus it is only possible to make samplings or examinations easily ina vertical direction from the opening. In order to proceed elsewhere,the end of the cable is pushed aside guiding it by rods engagedobliquely through the opening, which is time-consuming, not veryprecise, can present dangers and in general does not allow access to theedges of the silo whose width is often about ten meters.

SUMMARY OF THE INVENTION

The device according to the invention has the aim of making up for thesedefects and in particular to make it possible to carry out examinationsor samplings of the contents of the silo easily at any point whatsoever,and to guide the mechanism lowered under the slab with great precision.The device according to the invention also has other advantages in thatit does not require any human intervention under the slab or near theopening, and in that it is sufficiently sturdy not to need anything butinfrequent maintenance, which is essential for the principal applicationenvisaged concerning radioactive waste. It is characterised in that itcomprises at least three guide cables situated under the slab,converging onto a guide means with hollowed out periphery, in the formof a cross or a star, located under the slab, to which they are attachedcrossing the slab by drilled holes located at the edge of the silo, androlled onto winches operated by motors, a common control system for thewinches, and in that the crosspiece is provided with surfaces forsliding the support cable between the attachment points and the guidecables.

Thus, the rolling up of the guide cables, each of them controlledindependently by the control system, makes it possible to displace thecrosspiece, as well as the support cable, which has previously been lefthanging against a suitable face of the crosspiece between two anchorpoints of the guide cables. The examination or sampling mechanism isthen pulled above the desired position, and then it suffices to lower itso that it arrives over the sample. Advantageously there can be fourguide cables, the drill holes by which they pass under the slab beingarranged in a rectangle, at the corners of silos of this same shape,which makes it possible to move the crosspiece anywhere under the slab.

The invention can be perfected in many other ways. Some have theobjective of guaranteeing the precision of the displacement of thecrosspiece. The winch motors can then be equipped with sensors measuringforce, linked up to the control system, in order to evaluate thelengthening of the cables due to the traction and in consequence torectify the motor commands; the drill holes can be equipped with sleevescarrying rollers defining a curved guiding device, in which a respectiveguide cable slides and which serves to orient it better towards thecrosspiece by making the sleeve pivot using a motor directed by thecontrol system. Finally, the winches can comprise drums with a hollowedsurface with a helicoidal reception groove for the guide cables to berolled in a single layer, which means that the rotation of the drumsalways unrolls the same length of guide cable.

Preferably the support cable is not submitted to excessive friction.Thus the crosspiece, the opening of the slab or both can be providedwith rollers on which the cable slides. Precise guidance of the supportcable is obtained if the surfaces of the crosspiece are concave whenlinking the hooking points of the guide cable, the sliding rollersarranged around the opening of the slab being arranged on a polygonaland turning crown.

One embodiment of the invention, given as a purely illustrative example,will be described with the help of the following figures and will makeit easier to understand its characteristics, aims and advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view of the device and its location,

FIGS. 2 and 3 are representations of the drill holes intended for theguide cable and also show adjacent equipment,

FIG. 4 is a single view of the support cable,

FIGS. 5 and 6 are views of the crosspiece to which the guide cables arehooked,

FIGS. 7 and 8 are views of the opening in the slab,

FIG. FIG. 9 is an enlargement of FIG. 8.

DESCRIPTION OF EXAMPLE EMBODIMENTS

A silo 1 is made from a cement envelope more or less cubic whose topforms a slab 2 (often called a “cover-slab”) where the invention isinstalled. Slab 2 is pierced by an opening 3 at its centre, which makesto possible to gain access to the pit 4 enclosed by silo 1 and throughwhich waste is tipped. In the most general situation, it is possible todistinguish a pile of solid waste 5 at the bottom of the pit 4 and alayer of liquid waste 6 which is higher than the solid waste; waste ofany consistency can evidently be tipped in and left to settle.

The opening 3 serves for introducing a grab 7, intended to take samplesof solid waste 5 and which here represents the tool for which theinvention is intended, but it is evident that many other tools couldreplace it according to the nature of the work to be done. The grab 7 issuspended from a support cable 8 rolled on a lifting winch 9. Four guidewinches 10 can be noted at the corners of the slab 2, from where therespective guide cables 11 are unrolled, passing under slab 2 aftercrossing through the drill holes 12. The guide cables 11 converge on apart in the shape of an cut-out crosspiece, here crosspiece 13, on whichthe support cable 8 slides. A control system 14 is linked to the winches9 and 10 to give commands: the correct rolling and unrolling of theguide cables 11 makes it possible to move the crosspiece 13 at willunder the slab 2, as well as the grab 7 which hangs beneath it; andcontrol of the support cable 8 makes it possible to lower or lift thegrab 7, particularly when it overhangs the desired sampling point. Thecontrol system 14 comprises a computer linked to the motors and controlsensors of the winches 9 and 10; supplementary details about the controlprocedure will be given below.

FIG. 2 represents a front view of a guide winch 10. Its motor isreferenced 15 and drives the horizontal rotation axle 16 of a drum 17 bya kinematic linkage comprising a reducer 18, a torque limiter 19 and asensor 20 for measuring torque. The aim of the torque limiter 19 is toprevent imposing too high a traction on the guide cable 11 by uncouplingthe motor 15 and, if one so wishes, the sensor 20 makes it possible toevaluate the lengthening of the guide cable 11 consecutive to thistraction; it is thus linked to the control system 14. Finally, the axle16 is provided with a resolver 21, or another sensor capable ofmeasuring the rotation angles and thus the rolling and unrolling of theguide cable 11. The motor 15 and its output shaft (coaxial with axle 16)are supported by bearings 22 of a frame 23 fixed on the slab 2, and therotation axle 16 of the drum 17 is mounted on another pair of bearings24 of another frame 25, also fixed on the slab 2. The drill hole 12 isequipped with a sleeve 26 whose first function is to re-establish theseal of slab 2 at this point and, for this, comprises a first washer 27at its lower extremity and a second washer 28 at its upper extremity.Nonetheless the guide cable 11 has to pass through the sleeve 26 and thewashers 27 and 28; this is why these two washers are provided withdiametral slits 29 and 30, which are arranged in such a way as to crosseach other in order to avoid radiation originating from the waste 5 and6 crossing through the drill hole 12 too easily. Another aim of the slit30 of the upper washer 28 is to allow the guide cable 11 to pass throughwithout friction, whatsoever the part of the drum 17 from which it hasbeen unrolled: it is thus parallel to the unrolling edge of the drum 17.A crossbar 31, called an anti-run-back, is placed against this unrollingedge so as to apply the guide cable 11 by pressure, for a reason whichwill be explained below.

The mounting of the guide cable 11 in the sleeve 26 can be accomplishedin practice by basing it on a generatrix 32 taking care that the washers27 and 28 can rotate on it. The edges of the slits 29 and 30 and thegeneratrix 32 are then aligned before engaging the guide cable 11 in thesleeve 26; next the washers 27 and 28 are turned to cross the slits 29and 30.

FIG. 3 is a side view of the same parts, but it will serve essentiallyto illustrate the sleeve 26 in detail.

The lower washer 27 carries a return box 33 composed of rollers 34 inthe form of a dual wheel which defines a groove 35 between them andthrough which the guide cable 11 passes. The groove 35 is curved, with avertical upper extremity and a horizontal or oblique lower extremity, inorder to allow the guide cable 11 to change from a vertical length,where it crosses drill hole 12 to an oblique or horizontal length underthe slab 2 where it remains sufficiently high above the level of theliquid waste 6. The return box 33 should be directed towards thecrosspiece 13: the sleeve 26 is then set on the slab 2 in such a way asto pivot, and a motor 36, mounted on a frame 37 fixed to the slab 2,drives it by the intermediary of a reducer 38, a pinion 39 and a toothedcrown 40 mounted on the periphery of the sleeve 12. An encoder 41informs the control system 14 of the movements made by the sleeve 26.Reference 42 shows a handle fixed to the upper washer 28 which makes itpossible to extract the sleeve 26 from the drill hole 12 or to let itdescend. Finally, it is to be noted that the rotating and extractablesleeve 26 is engaged in a fixed sleeve 71 coating the drill hole 12 andthat there is an intermediary sleeve 72 slipped between them. Thisintermediary sleeve 72 pivots inside the fixed sleeve 71 by sliding on apair of O-rings 73; in addition, there is play between the sleeve 26 andthe intermediary sleeve 72. Thus, the return box 33 is made to rotate bythe guide cable 11 and this drives the sleeve 26 and the intermediarysleeve 72, which pivots with little friction on the fixed sleeve 71.Stops 74 make it possible to stack the sleeve 26 on the intermediarysleeve 72. Lugs 75 engaged in a circular groove of the fixed sleeve 71enable it to prevent the intermediary sleeve 72 from falling into thepit 4.

The lifting winch 9 of the support cable 8 is shown in FIG. 4. It alsocomprises a drum 43 with horizontal rotation axles 44 mounted on a pairof bearings 45 of a frame 46 fixed on the slab 2, and a motor 48 drivesthrough the intermediary of a reducer 49. An encoder 50 makes itpossible to measure the rotations of the axle 44 and to transmit this tothe control system 14. The motor 48 is also supported by bearings 51, onpart of the frame 46.

An essential element of the construction is that the drum 43 has itsoutside surface notched by a helicoidal groove 52 intended for rollingthe support cable 8 in a single layer, which then follows the groove 52along the drum 43 when it is rolled. An antislip crossbar 53 analogousto that 31 of the guide winches 10 ensures this function by pressing thelifting cable 8 as soon as it approaches the groove 52 and thus forcingit to follow its oblique direction. It is to be noted that suchhelicoidal grooves already exist but in general their aim is to preventwhat is called the build-up (tangling) of a cable unwound at great speedand of great length, in arranging its first layer and then each of thefollowing ones so that they are evenly superposed; cables 8 and 11 aremuch shorter here and the intended aim is simply to spread them in asingle layer so that one turn of the drum 17 or 43 unwinds onedetermined and unchanging diameter coil of cable.

In this embodiment of the invention, the support cable 8 is unrolled atthe same time as a pipe 54 providing fluid to the jacks 55 fordisplacing the claws 56 of the grab 7. The pipe 54 is linked to a fixedpipe 57 by the intermediary of a rotating joint 58 prolonging the axle44 and next to the drum 43. The ensemble constituted by the liftingcable 8 and the pipe 54 is more easily subject to damage and moredifficult to guide than a single cable, which means that supplementaryprecautions have to be taken as herein to solve this problem.

The crosspiece 13 is seen from above in FIG. 5. It is composed of fourappendices 59 directed towards the guide cables 11 and terminated byvertical rings 60 pivoting around a vertical axis 61, in which the loops62 at the ends of the cables 11 are engaged. This mounting makes itpossible to direct the crosspiece 13 with high precision. In addition,the appendices 59 are provided with rollers 63 on their upper faces, aswell as the body 64 of the crosspiece 13 which unites the appendices 59together. These faces are convex so that the support cable 8 rests onthe rollers 63 along a suitable length, as FIG. 6 shown as across-section through one of the arms 59 makes perfectly clear; inaddition, care has to be taken to shape these sliding surfaces of thesupport cable 8 with concavities between appendices 59 adjacent to thehooking of the guide cables 11, in such a way that the support cable 8in encouraged to enter into the bottom of one of the grooves 65 thusformed and to remain there even when there are oscillations: it is thenplaced with high precision on the crosspiece 13 and slides withoutexcessive friction.

Finally there is the description of FIGS. 7 to 9 which represent thetrimming of the opening 3 of the slab 2. Normally a cement cover closesthe opening 3 but it is withdrawn when the invention is to be used. Thenone can see an octagonal crown 67 appear, which encircles the opening 3.This crown 67 turns on a circular bearing surface 68 of the slab 2provided with two ball bearing circles 69 directed upwards and downwardsand which support the crown 67 by keeping it at a constant level,eventually preventing it being lifted when the support cable 8 undertension passes under it, and the sides of the octagon are defined bygroups of rollers 70 superposed in receding positions towards thebottom, so that they are further and further from the centre of theopening 3. If the grab 7 has to be directed towards the sides of the pit4, the support cable 8 is pulled towards the crown 67 until it touchesthe rollers 70 on one of its sides; it then slides along them easily andwithout friction with the slab 2; the crown 67 rotates to reducefriction with the support cable 8 and wear of the latter. Generally, thesupport cable 8 slides up to the angle of two sets of neighbouringrollers 70 and remains there until the end of the procedure,consequently controlling the rotations of the crown 67 to follow itsmovements: the friction of the support cable 8, which would have beensignificant if it had slid against the periphery of the opening andwould have hindered correct unrolling, thus becomes very slight.Reference 66 defines a funnel covering the crown 67 and the bearingsurface 68 and protects them against runoff.

The operation of the device can be described fairly simply: once it hasbeen decided to take the grab 7 to a defined point in the pit 4, it islowered slightly through the opening 3 after having placed thecrosspiece 13 not far from it, in such a way that the support cable 8passes in front of the groove 65 which is directed towards the positionto be reached. Then certain guide cables 11 are rolled up while othersare unrolled to displace the crosspiece 13 in such a way as to place thesupport cable 8 in the chosen groove 65 and then to move the grab 7towards the chosen position; these movements are accompanied byprogressive unrolling of the support cable 8 to prevent the grab 7rising up to the crosspiece 13; the control system 14 constantlycalculates the length of each of the guide cables 11 thanks to theinformation from the resolvers 21, then the position of the crosspiece13 and that of the grab 7; it also orients the sleeves 26. It can takeinto account the lengthening of the guide cables 11 consecutive to theirtraction and of the position of the groove 65 on which the lifting cable8 slides, to improve the calculation of the position of the grab 7. Ittakes care not to apply excessive force on the guide cables 11; howeverthe torque limiters 19 make it possible to avoid excessive traction andto relax the cables 11 until the traction has disappeared. When the grab7 overhangs the position required, the control system 14 continues toactuate the lifting winch 9 until the grab 7 has been lowered to theheight required; it takes into account the length of support cable 8which has already been unrolled and which has been indicated by theencoder 50. The jacks 55 can then be put into action to close the claws56 and seize a sample of the waste, after which the preceding operationsare repeated in reverse to bring the grab 7 back underneath the opening3 and to lift it up.

1. A device for examination, sampling or extraction of the contents of asilo (1) located under a slab (2) pierced by an opening (3), by an organsuspended from a support cable (8) and lowered through the opening (3),comprising at least three guide cables (11) located under the slab (2),converging towards a guide means (13) to which they are hooked athooking points by crossing the slab (2) by drill holes (12) arranged ina crown and rolled on winches (10) driven by motors, a common controlsystem (14) for the winches (10, 9), the guide means being provided at aperiphery thereof with concavities (65) for the support cable whichalternate with the hooking points (60) of the guide cables (11), theconcavities (65) of the guide means being defined by at least onesliding surface (63) and being concave when linking the hooking points(60) of the guide cables.
 2. A device according to claim 1,characterised in that the motors (15) of the winches (10) are providedwith force limiters (19).
 3. A device according to claim 1,characterised in that the motors of the winches are provided with forcemeasurement sensors (21) linked to the control system (14).
 4. A deviceaccording to claim 1, characterised in that the support cable (8) isrolled onto a winch (9) driven by a motor (48) directed by the controlsystem (14).
 5. A device according to claim 1, characterised in that thedrill holes (12) are provided with a sleeve (26) provided with a washer(27) with an opening (29) for the passage of a respective guide cable(11).
 6. A device according to claim 5, characterised in that the washer(27) carries rollers (33, 34) defining a guide groove of a respectiveguide cable (11).
 7. A device according to claim 6, characterised inthat the groove is curved and comprises a vertical extremity towards thewasher (27) and an oblique extremity directed towards the guide means(13).
 8. A device according to claim 7, characterised in that thesleeves (26) are mounted on the slab so as to pivot, and are driven bymotors (36) directed by the control system.
 9. A device according toclaim 5, characterised in that the sleeves comprise a second washer (28)with an opening for the passage of a guide cable, the openings (29, 30)of the washers being crossed slits.
 10. A device according to claim 1,characterised in that the winches (9, 10) comprise drums (17, 43) with asurface cut out with a helicoidal groove (52) for reception of thecables (8, 11) in a single rolled layer.
 11. A device according to claim10, characterised in that the winches comprise crossbars (31, 53) forpressing on the guide cables, set against the drums.
 12. A deviceaccording to claim 1, characterised in that the guide cables are fourand the drill holes (12) are arranged in a rectangle.
 13. A deviceaccording to claim 1, characterised in that the guide cables are hookedto a guide means by engagement of an loop (62) in a ring (60).
 14. Adevice according to claim 1, characterised in that the sliding surfaces(63) of the guide means (13) are provided with rollers (63) and areconvex in the vertical direction.
 15. A device according to claim 1,characterised in that the opening of the slab is provided with a crown(67) of rollers (70).
 16. A device according to claim 15, characterisedin that the crown of rollers is polygonal and mounted on the opening (3)of the slab (2) in such a way as to turn freely.
 17. A device accordingto claim 16, characterised in that the crown of rollers is recedingdownwards and mounted on the opening of the slab with upward anddownward supports (69).